This invention relates to flame retardant nylon compositions having improved physical properties and excellent molding characteristics.
Nylons represent a family of commercially available polymers characterized by the presence of recurring amide groups in the polymer chain and generally noted for their excellent physical properties for a variety of end uses, including the formulation of molding compositions. Nylon 6, produced by polymerization of .epsilon.-caprolactam and Nylon 66, produced by the condensation reaction of adipic acid and hexamethylenediamine account for the major share of commercial nylon molding compositions.
It is known that the fire retardancy of some nylon compositions may be enhanced by the incorporation therein of various chlorinated organic fire retardants, often in combination with a suitable metal oxide, such as a zinc or antimony oxide. A particularly effective fire retardant for Nylon 6 and Nylon 66 is 1,4,7,10-dimethanocycloocta-1,2,3,4,7,8,9,10,13,13,14,14-dodecachloro-1,4, 4a,5,6,6a,7,10,10a,11,12,12a-dodecahydro[1,2,5,6] dibenzene, characterized by the formula: ##STR1## (For convenience, this compound will be referred to herein by the shorter title of bis(hexachlorocyclopentadieno)cyclooctane. The incorporation of bis(hexachlorocyclopentadieno)cyclooctane, optionally in combination with a suitable metal oxide, in nylon compositions, is disclosed in U.S. Pat. No. 3,403,036 to Hindersinn et al. It is known that such nylon compositions are characterized by excellent fire retardant properties and are generally satisfactory to excellent with respect to most of the desired physical properties sought in nylon compositions. However, it has been found that the incorporation of the aforementioned additives in Nylon 6 or Nylon 66 molding compositions results in an increase in the melt viscosity with a consequent decrease in the ease of processing in molding operations.
Accordingly, it is an object of this invention to provide nylon compositions particularly suited for use in molding processes. It is a further object to provide fire retardant nylon compositions characterized by improved processibility in molding operations, especially in injection molding operations, and improved physical properties of the final molded product.